In modern motor cars hydraulic oscillation dampers are provided which permit variation of the damping behaviour. Such hydraulic oscillation dampers are provided with an electromagnetically controlled valve unit. This valve unit is provided in a flow path connecting two working chambers the volume of which is altered in opposite senses during movement of a piston rod with respect to the container of the respective oscillation damper. This flow path is in parallel with a continuously open throttled flow path. By variation of the cross-sectional area of the flow path through the electromagnetically controlled valve unit, the damping behaviour of the oscillation damper can be varied. The variation of the damping behaviour may be a continuous or a step-wise variation. The electromagnetically controlled valve unit is preferably fastened to the outer side of a container of the oscillation damper. Electromagnetic and fluidic components of the valve unit are accommodated within a compartment attached to the outer side of the container.